This invention relates generally to measuring tapes used to determine the proper lengths for roof framing members to be cut when framing roofs. More particularly, the invention relates to such tapes which provide secondary scales for determining the length of common rafters, hip rafters, valley rafters, jack rafters and the rise height. Even more particularly, the invention relates to such tapes where the secondary scales provide indicia means for directly marking the proper length of the appropriate rafters to be cut, without requiring further manipulation, calculation, or reference to a pre-calculated table by the user.
When constructing a roof, sloping frame members known as rafters provide the supporting framework. The common rafters slope from the exterior wall top plate to the face of the roof ridge. Common rafters are attached at right angles to the top plate and the ridge member. Where two sloped roofs meet at an inside corner, a valley rafter runs between the two roofs from the top plate to the junction of the two ridge members. Where a hip roof forms part of the roof, a hip roof referring to a roof construction having a sloped end as well as sloped sides, formed when two adjacent sloping roof sides meet, hip rafters slope from the top plate corners to the ridge. Hip jack rafters join the top plate to the hip rafter, and valley jack rafters join the ridge to the valley rafter. Determining the proper length of the common, valley, hip and jack rafters requires use of the Pythagorean theorem. To determine the proper length for a common rafter, for example, the horizontal distance from the point beneath the outer face of the ridge member to the top plate is determined, the vertical distance beneath the ridge is determined, and then the particular rafter length is calculated. Such calculations are typically beyond the ability of construction workers or are overly time consuming, so printed tables containing previously calculated values for various roof pitches are usually consulted to ascertain the proper length to cut the rafters. To determine proper lengths for the hip, valley and jack rafters, the calculations are even more complicated, and again reference tables must be consulted.
Various devices have been conceived in attempts to provide a measuring tape which can be used to determine proper roof framing member lengths without having to consult tables on site. For example, an early attempt by Dahmer is shown in U.S. Pat. No. 499,621. This device is a scale in the nature of a slide rule and is essentially a table in a non-paper format. The run of the rafter, the horizontal distance, is determined by measurement with a standard measuring rule and a slide is positioned at the appropriate corresponding indicia on the central scale. Values for the common, hip or valley rafters are then read from one of the other scales. This value is then measured out on the board to be cut using a regular tape measure. This device is not very precise and requires proper alignment of the slide to insure a correct end result.
Martin in U.S. Pat. No. 1,643,166 shows a device in which incorporates tables on the back of a conventional measuring tape. This device requires the worker to properly read and compute from the tables the proper length for the rafter to be cut. As in the Dahmer device, this is merely a new format for a table and still requires calculations by the worker.
Norton in U.S. Pat. No. 3,289,305 shows a measuring tape which incorporates a slide and curved pitch lines. This device requires the worker to memorize several steps for determining correct lengths, as the device also utilizes a number of scales, marking indicia and movement of the slide. These steps are complicated and provide ample opportunity for error.
It is an object of the invention to provide a measuring tape device for correctly determining proper rafter lengths for common, hip, valley, hip jack and valley jack rafters, which does not require the use of tables, calculations or manipulation of slides.
It is an object to provide such a device which indicates the proper rafter lengths without need for any other equipment or tapes.
It is an object to provide such a device where the indicia for correctly marking the rafter board to be cut are physically located on the tape at the actual distance from the tape end where the board is to be cut, whereby the proper length can be marked directly onto the board.